The present invention relates to an improvement of a machine for manufacturing circular section helical wave guides for transmission of electromagnetic energy in the circular TE 01 mode in preference, to the exclusion of all other modes.
A known type of machine for manufacturing such wave guides employs a first manufacturing phase in which a helical conductor is made by welding turn by turn of a helix formed from a conductor wire which has a covering of low loss material. In a second phase this helix is inserted into a conductive metal envelope which serves as a screen for the guide, the envelope being drawn down around the helix in such a manner as to hold the turns in place with very slight play to avoid altering their inner diameter.
However, a guide made according to this method suffers from drawbacks. Indeed, the separation between the screen and the helix introduces an eccentricity which results in a lowering of the maximum operating frequency. Further, when the guide is curved to change direction during laying, part of the electromagnetic energy leaks through the turns and the eccentricity reduces the uniformity of transmission by the helix.
Preferred embodiments of the machine according to the present invention reduce this drawback. Indeed it is possible to arrange at the same time both for the inner surface of the helix to be uniform and for the metal envelope to be brought into close contact with the outer surface of the helix.